Assuming a 6max cash game where i am big blind. in this position do i have an edge over sb ? i know that against all other positions i never print because i am out of position. what about Big vs Small?

You have the positional advantage, so you can profitably play a wider range against the SB than against any other position. He's also playing a wider (and thus weaker) range than anyone else, since he only needs to beat one player. (Someone who opens UTG can only steal the blinds if 5 people fold, so he/she needs to start with a strong range that has a decent chance of winning against the whole table. The SB only needs the BB to fold).

what i want to know is who is wining assuming both players play gto. BB or SB ?
BB has postion but also has a posted blind while sb only have half of a blind.

Your asking a specifically-impossible-to-answer question other than what Arty answered.

If you have two equally matched opponents, the one with a positional advantage will ALWAYS* win out over the long run.

*(please don't use absolutes in poker like Always and Never because there will usually be statistically possible outcomes that disprove Always/Never)

* in two blind games.

If we're talking strategy vs strategy ev, then the big blind is going to be the big winner here, but that doesn't mean that the small blind's strategy is inherently -ev. Because of the money in the pot, and the ability to make plays with positive expectation, both strategies are going to show a long term profit.

If we're talking about small blind opening range ev, then this value will be even higher than the value found for the small blind's entire strategy; without the hands that fold preflop involved in the calculation, we see a higher net +ev for the small blind.

If we're talking about the ev of individual hands, then we need to break the small blind's range into groups: assume 3x raise:

a) monsters = these hands own part of the big blind's stack in addition to the 1.5bb in the existing pot. I'm thinking QQ+, AK.

b) strong hands = these hands earn a large fraction of the 1.5bb in the existing pot. I'm thinking 77-JJ, A8sQs, AJo, AQo, KJs+, QJs, etc.

c) semi strong hands = these hands earn a smaller fraction of the 1.5bb in the existing pot. I'm thinking 22-66, A2s-A7s, K5s-KTs, Q9s, QTs, etc.

d) slightly profitable but weak hands = these hands earn a very small fraction of the 1.5bb in the existing pot in large part due to preflop fold equity. Without this preflop fold equity contributing to the profit margin, these hands will cease to be profitable. I'm thinking K4s-, Q8s-, J8s, etc.

note that all groups except (a) actually prefer that the big blind folds in order to earn the most long term profit, or the 1.5bb in the existing pot.

SB has to put a full BB in to play a pot do they not?

Yes, SB can fold and only lose half a blind, but then guess who wins.

I'm thinking about this in simple terms here but it seems to me BB has the obvious advantage BvB

I think the GTO solution is to not play, since the game is already at an equilibrium state (with the SB on 99.5bb, the BB on on 99bb, and 1.5bb in the middle). The BB wins money when the SB gives him a walk, but if the SB has a playable hand and decided to play it, the best his range can do against a GTO opponent is break even in the long run. Similarly, if the SB does play a hand, BB responds with a strategy that also breaks even against the SB's strategy.
If the SB wins the first hand, he should probably hit and run, a la Grimstarr.

If two GTO bots simulated this situation billions of times, I'm not sure what proportion of pots that the BB would win, but the SB can only play about 60% of hands even if he uses a limping strategy, so the BB is gonna win a ton of money from walks.

Depends on the player on the button mostly and how that player affects your overall winrate. You're definitely taking a loss by having to post your small blind, while the big blind actually owns part of your small blind as soon as it folds to you in the small blind.

However, I'm glad you didn't stop there because this is a common spot.

I think this is wrong. If both players are playing correctly then that means that they are making nothing but +ev decisions. Thus they chop up the money in the pot.

So for example:

folds to me in the small blind, I raise 3x with some ok range.

stop the action there and think about the pot:

there's 1.5bb dead money, and I'm investing 2.5bb with profitable raising hands. Thus I expect to win back on average some value above 2.5bb but not higher than 4bb, because the big blind has the opportunity to make profitable decsisions too.